Method and apparatus for mitigating an overload in a network

ABSTRACT

A method and apparatus for managing an overload condition in a network are disclosed. For example, the method monitors the network for a traffic overload condition, and determines whether a more severe traffic overload condition or a less severe traffic overload condition is detected by using a network monitor and controller. The method then selects using a network monitor and controller agent in response to a command from the network monitor and controller, a different bandwidth preservation scheme if the more severe traffic overload condition or the less severe traffic overload condition is detected, wherein the different bandwidth preservation scheme is based on a selection of a codec type and is applied to a portion of the traffic.

This application is a continuation of U.S. patent application Ser. No.12/772,939, filed May 3, 2010, now U.S. Pat. No. 8,495,205, and isherein incorporated by reference in its entirety.

The present disclosure relates generally to communication networks and,more particularly, to a method and apparatus for mitigating an overloadin a packet network, e.g., an Internet Protocol (IP) network.

BACKGROUND

A large scale service provider network, e.g., a Next Generation Network(NGN), typically consists of multiple regional access offices and serveroffices connected to a backbone network, e.g., via uplinks between pairsof provider edge (PE) and customer edge (CE) routers. NGN access officescan be deployed with session border controllers (S/BC) to providesecured access by user endpoint devices (UEs) from public accesses andPSTN media gateways (MGW) for connectivity with Time DivisionMultiplexing (TDM) based telephony networks. Server offices can bedeployed with call servers such as Call Session Control Functions(CSCF), Home Subscriber System (HSS), various application servers, mediagateway control functions (MGCF), etc.

Public networks provide connectivity from UE to the public interfaces ofS/BC. An NGN operator's internal backbone network providesinter-connectivity for communications of all other network elements.Some part of these networks may have more limited transport resourcesthan others. For example, the link bandwidth between PE and CE routersfor access offices are crucial network resources for providing the NGNservices to its subscribers.

NGN operators may size the link capacity based on the forecastsubscriber number, bandwidth per call, various historical call volumeparameters, and so on. However, some situations may cause dramaticincrease of call volumes. For example, events such as natural disasters,e.g., earthquakes, can trigger massive calling events. Since it is notpossible to deploy additional transport resources on the fly, theexisting network resources can be overloaded, thereby compromising theservice capability of the NGN network.

In addition to the massive calling events, a NGN is often designed withgeographical redundancy. Subscribers who are normally homed at oneaccess office or data center can be re-homed to another access office ordata center if their home office is out of service. This event will alsocause a dramatic increase of workload and traffic in the protectionsite.

SUMMARY OF THE DISCLOSURE

In one embodiment, the present disclosure describes a method andapparatus for managing an overload condition in a network. For example,the method monitors the network for a traffic overload condition, anddetermines whether a more severe traffic overload condition or a lesssevere traffic overload condition is detected by using a network monitorand controller. The method then selects using a network monitor andcontroller agent in response to a command from the network monitor andcontroller, a different bandwidth preservation scheme if the more severetraffic overload condition or the less severe traffic overload conditionis detected, wherein the different bandwidth preservation scheme isbased on a selection of a codec type and is applied to a portion of thetraffic.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present disclosure can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an NGN network related to the present disclosure;

FIG. 2 illustrates an exemplary network related to the presentdisclosure for mitigating an overload in a network;

FIG. 3 illustrates an exemplary network with one embodiment of thepresent disclosure for mitigating an overload in a network via acentralized network monitor and controller (NMC);

FIG. 4 illustrates a flowchart of a method for mitigating an overload ina network;

FIG. 5 illustrates a state transition diagram; and

FIG. 6 illustrates a high-level block diagram of a general-purposecomputer suitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present disclosure broadly teaches a method and apparatus formitigating an overload in a network. Although the present disclosure isdiscussed below in the context of an IP Multimedia Subsystem (IMS)Network, the teachings of the present disclosure are not so limited.Namely, the teachings of the present disclosure can be applied to otherpacket networks, e.g., Voice over Internet Protocol (VoIP) networks andthe like.

FIG. 1 illustrates an exemplary next generation network (NGN) 100related to the current disclosure. In one embodiment, the NGN 100comprises access offices 121-124, server offices 131 and 132, a publicnetwork 111 and an internal network 112. It should be noted that thenumber of access offices and server offices illustrated in FIG. 1 isonly illustrative.

Network addresses (e.g., router addresses) within the internal network112 are reachable using routing information available only within theservice provider's network. The public network 111 comprises the networkportion reachable using routing information (e.g., IP addresses)available in the public domain. Connections through the public network111 are referred to as public connections. Connections through theinternal network 112 are referred to as internal connections.Specifically, connections 199 a through 199 j are public connections.Connections 198 a through 198 d are internal connections.

Server offices are used for hosting various network devices such asMedia Gateway Control Functions (MGCFs), Application Servers (ASs), HomeSubscriber Servers (HSSs), Call Session Control Functions (CSCFs), etc.For example, server office 131 may host MGCF 141, Application Server142, HSS 143 and CSCF 144. Similarly, server office 132 may host MGCF151, Application Server 152, HSS 153 and CSCF 154.

Access offices are used for hosting network devices such as Proxy-CallSession Controller Functions (P-CSCFs), Session Border Controllers(S/BCs), Media Gateways (MGWs), Customer Edge (CE) routers, etc. in adistributed manner. For example, access office 121 may host P-CSCF 161,S/BC 162, MGW 163 and CE router 164, and whereas access office 122 mayhost P-CSCF 171, S/BC 172, MGW 173 and CE 174. Similarly, access office123 may host P-CSCF 181, S/BC 182, MGW 183 and CE 184, and whereasaccess office 124 may host P-CSCF 191, S/BC 192, MGW 193 and CE 194. Itshould be noted that an access office may host any number of mediagateways, P-CSCFs, S/BCs, CEs, and so on. In addition, the number andtype of devices hosted at each access office may be different.

In one embodiment, each access office 121-124 is connected to an IPbackbone network over both public and internal connections. For example,packets from IP UEs 101-110 reach an access office 121, 122, 123 or 124via the public network 111. For example, UE 101 may send registrationrequests to S/BC 162 in the access office 121 via public connection 199a. Similarly, each of the UEs 102-110 may send registration requests toS/BC 162, 172, 182 or 192, respectively via a public connection throughthe public network 111.

In one embodiment, the Session Border Controllers (S/BCs) are used toenable IP UEs to connect to the NGN 100 and obtain services. Forexample, a UE may register to the NGN via a particular S/BC to receiveVoIP services. Each S/BC bridges between the public network 111 and theinternal network 112. Once a UE registers to the NGN via a particularS/BC, calls to/from the UE flow through the particular S/BC throughwhich the UE is registered. The particular S/BC performs the bridging ofthe call between the public and internal networks.

In one embodiment, the MGWs are used to support calls between IP basedUEs and TDM based PSTN phones. Calls to or from a PTSN phone use aparticular trunk group on a particular MGW, depending on the PSTNnumber. The PSTN number refers to a phone number. For example, in phonenumbers derived from the North American Numbering Plan (NANP), the phonenumber is a 10 digit number. The area code is the first three digits,and is also referred to as a Number Plan Area (NPA) code. The termNPA.NXX refers to the first six digits of a phone number containing theNPA code and a three digit exchange number following the NPA code. Callsto and from a particular NPA.NXX may be routed via a particular trunkgroup on a particular MGW.

FIG. 2 illustrates an exemplary network 200 for mitigating an overloadin a network. The network 200 comprises access offices 121 and 124,server offices 131 and 132, a public network 111, an internal network112, Public Switched Telephone Networks (PSTNs) 213 and 214. Forexample, a TDM UE 215 reaches the access office 121 via the PSTN 213.Similarly, a TDM UE 216 reaches the access office 124 via the PSTN 214.It should be noted that this description pertains only to the media pathfor an active call session. Furthermore, it should be noted that this isan illustrative network configuration in which there is a differencebetween access offices and server offices. However, other NGN operatormay choose to deploy differently by dividing the NGN into many regionaloffices where the server office equipments and access office equipmentsare combined together. Thus, the present disclosure is not limited inthe manner the access offices and server offices are illustrated.

In one embodiment, the current method teaches mitigating an overload ina network by controlling and/or changing a type of codec used for calls.In one embodiment, the method first identifies network transport nodesthat function as critical gateways, e.g., CEs, PEs, S/BCs, etc. Themethod may then deploy one or more Network Watch Points (NWPs) andNetwork Monitor and Controllers (NMCs), as described below.

In one embodiment, the network 200 comprises a Network Monitor andController in each access office. The network 200 also comprises NMCagents deployed in MGCFs in the server offices throughout the NGN. Thenetwork 200 also comprises one or more Network Watch Points or modules,at various points of an NGN network, e.g., PE routers or CE routers, orS/BCs of an NGN. The functions of the NMCs and NWPs will be describedbelow.

In one embodiment, an NWP refers to a module in a network device that isused for determining when a bandwidth usage in a node either reaches orexceeds a predetermined threshold. In turn, the NWP may also be used toalert the NMC when the bandwidth usage has either reached or exceededthe predetermined threshold. For example, the method may deploy an NWPat each of the identified CE, PE or S/BC nodes.

In one embodiment, an NMC refers to a network device or a module that isused for gathering alerts from the NWPs and for controlling networktraffic volumes. The NMC comprises at least a policy rule engine fordetermining one or more actions for controlling traffic load. Forexample, the policy rule engine may decide when to force the use of alower bandwidth coder/decoder (codec) on new calls, when to use amidcalf procedure to change codecs for existing calls, and when to stopenforcing the use of the lower bandwidth codec, as described below.

In one embodiment, the NMC may operate with the NMC agents implementedin various Media Gateway Controller (MGC) functions. That is, softwaremodules which function as NMC agents may be implemented in MGCfunctions. The NMC may then interface with the NMC agents in one or moreMGCFs to control traffic load, i.e., to take appropriate actions uponreceiving commands from the NMC, as discussed further below.

In one example, an NWP in a node may determine that the bandwidth usagefor the node, e.g., a CE, a PE, a S/BC and the like, has exceeded apredetermined threshold, e.g., 90% of capacity, 80% of capacity, and soon. The NWP will then alert the NMC that the threshold has been reachedor exceeded. The NMC gathers the alerts and then activates one or moresteps of the current disclosure to control the traffic load bycontrolling and/or changing a type of codec used for calls. It should benoted that any description pertaining to numerical values in the presentdisclosure, e.g., a particular threshold value, is only illustrative.The scope of the present disclosure is not limited to any particularnumerical values, and the present disclosure can be adapted to meet therequirements of a particular implementation.

In one embodiment, e.g., in a distributed implementation, there is oneNMC in each access office. Each NMC receives reports from the NWPs forvarious network resources supporting that particular access office. Whenit detects any surges of network resource usage from one or more NWPs,the NMC may send a command to one or more NMC agents deployed in variousMGCFs throughout the network such that the one or more MGCFs may takeappropriate action to control traffic to address an overload condition.For example, if the NMC in an access office receives a surge of networkusage from one or more NWPs for a specific rate center served by theparticular access office (e.g., as identified by an NPA of NPA-XXXcode), the NMC may send a command to the NMC agents in the MGCFs tocontrol traffic load by using a codec that requires a lower bandwidth.The various MGCFs may then continue to support calls using a codec witha lower bandwidth in accordance with the command received from the NMC.

For example, voice data transmission using a standard InternationalTelecommunications Union (ITU) G.711 codec may have a codec bit rate of64 Kbps, while voice data transmission using an ITU G.728 codec may havea bit rate of 16 Kbps. The present method may then lower the bandwidthneeds to support each call by up to a factor of four by changing from aG.711 codec to a G.728 codec as an example. It should be noted that thisis only one illustrative example. The present disclosure is not limitedto any particular types of codecs.

In one embodiment, the commands sent by the NMC to the NMC agents in theMGCFs to control traffic load may vary based on a threshold that isreached. For example, there may be a plurality of threshold levels(broadly referred to as overload condition severity levels) such as“green”, “yellow”, “orange”, “red”, etc.

For example, the threshold associated with the green level may indicatethat there is no overload condition. If a command to use a lowerbandwidth codec was previously issued, the NMC may send another commandto the NMC agents to terminate enforcing the previously issued commands,i.e., stop enforcing the use of a lower bandwidth codec. If there was nopreviously issued command, i.e., while the network condition is still atthe green level, the NMC simply continues the monitoring.

The threshold associated with the yellow level may indicate that anoverload condition has been detected. In response, the NMC will issue acommand to enforce the usage of a lower bandwidth codec only for newcalls. For example, existing calls (calls in progress) may continue touse the codec selected when the call was established, while new callswill be supported using a codec with lower bandwidth. In other words,ongoing calls will not be affected with the codec change at this level.

The threshold associated with the orange level may indicate that a moresevere overload condition has been detected. In response, the NMC willagain issue a command to enforce the usage of a lower bandwidth codec.For example, the NMC may issue a command to initiate mid-call proceduresto change existing calls to a lower bandwidth codec. In other words, notonly new calls will use the lower bandwidth codec, but even existingcalls will use the lower bandwidth codec. For example, the method mayuse existing Session Initiation Protocol (SIP) mid-call controlprocedures to change the type of codec for calls that are already inprogress. For example, SIP provides mid-call changes such as, addinganother end-point to a conference, modifying a media characteristic,modifying a codec, and so on. The method may then invoke a SIP mid-callcontrol procedure to initiate usage of a codec with a lower bandwidthfor all existing calls.

In one embodiment, the red level may indicate that a very severeoverload condition has been detected. However, unlike the yellow leveland orange level, the red level may indicate that the overload conditionis so severe that changing the codec type may not adequately address theoverload condition. In response, the NMC will issue a command to executeother overload correction procedures, e.g., taking other correctiveactions that do not involve changing the codec type. For example, othermethods of reducing traffic including but not limited to throttling,blocking, etc. may be used. Thus, the present disclosure provides amethod of addressing traffic overload in a network in a scalable mannerwith a plurality of different actions that will alter the type of codecsthat are being used to address the particular overload condition that isbeing detected. This approach will allow the network to dynamicallyrespond to overload conditions very quickly in a cost effective way. Itallows the NGN network to be more adaptive to the network condition in adynamic manner. The NGN network implementing this method can supportmaximal possible call sessions under overload conditions that may becaused by mass calling events, office failover, etc.

It should be noted that the number of threshold levels and color codesis only exemplary. As such, the teachings of the current method are notintended to be limited to these exemplary implementations.

Returning to the exemplary network 200, server office 131 may host MGCFwith NMC agent 241, Application Server 142, HSS 143 and CSCF 144,whereas server office 132 may host MGCF with NMC agent 251, ApplicationServer 152, HSS 153 and CSCF 154. Access office 121 may host P-CSCF 161,S/BC with NWP 262, MGW 163, CE router with NWP 264 and an NMC 266.Access office 124 may host P-CSCF 191, S/BC with NWP 292, MGW 193, CErouter with NWP 294 and NMC 296. It should be noted that an accessoffice may host any number of media gateways, P-CSCFs, S/BCs, CEs and soon. In addition, the number and type of devices hosted at each accessoffice may be different. Each of the access offices 121 and 124 isconnected to an IP backbone network over both public and internalconnections.

For example, CE router 264 is connected to the public connections on aPE router 265 over a public link, and to internal connections on the PErouter 265 over an internal link. Similarly, CE router 294 is connectedto public connections on PE router 295 over a public link, and tointernal connections on the PE router 295 over an internal link. Itshould be noted that the separation of the PEs between internal networkand the public network is just a logical illustration. In oneembodiment, the PEs could physically be a single backbone router.

Packets from IP UEs 101 and 102 reach the access office 121 via thepublic network 111. For example, UE 101 may register to the NGN via S/BC262 in access office 121. Packets from UE 101 may then reach the S/BC262 in the access office 121 via the public connection 199 a. Similarly,UE 110 may register to the NGN via S/BC 292 in the access office 124.Packets from UE 110 may then reach the S/BC 292 in the access office 124via the public connection 199 j.

As discussed above, there are many causes that may trigger a suddenincrease of the resource consumption in a part or all of an NGN network.Mass calling events, such as those triggered by a natural disaster ornational security crisis, are one of the examples. Another example isthe situation referred to as access office failover.

To illustrate, if a call is between an IP based UE and a TDM based PSTNphone, then the call is handled by the S/BC at which the UE isregistered and the MGW handling calls to/from the PSTN phones for thespecific area code, i.e., NPA.NXX code. If the S/BC and the MGW for acall are collocated in the same access office, then the call traversesthe link between the PE router and the CE router once. If the S/BC andthe MGW for a call are located in different access offices, then thecall traverses the link between the PE router and CE router in theaccess office with the S/BC twice and the link between the PE router andCE router in the access office with the MGW once.

In one example, a call is originated by UE 101 registered via S/BC 262.The call is destined to a PSTN phone 215 and MGW 163 provides trunkgroup to the PSTN switch serving the rate center (NPA.NXX) for the PSTNphone 215. A bearer path 299 illustrates the media flow traversed byaudio packets to/from UE 101 and PSTN phone 215. The media floworiginated by UE 101 traverses PE 265 and CE 264 to reach S/BC 262. S/BC262 bridges the media flow to the internal network and forwards themedia flow to MGW 163 via CE 264. The MGW 163 may then forward the mediaflow to the PSTN phone 215 via the PSTN 213. It should be noted that onthe same call session between the two parties, there is another mediaflow in the opposite direction directed towards the UE101.

In another example, a call is originated by UE 101 registered via S/BC262. The call is destined to a PSTN phone 216 and MGW 193 provides trunkgroup to the PSTN switch serving the rate center (NPA.NXX) for the PSTNphone 216. A bearer path 297 illustrates the media flow traversed byaudio packets to/from UE 101 and PSTN phone 216.

As illustrated in the above example, when the S/BC and MGW for a callare in different access offices, twice as much bandwidth is required inthe access office with the S/BC, as compared to the bandwidth requiredwhen the S/BC and MGW are collocated. General phone call statisticsshows that the majority of phone calls are local calls. Accordingly,network service providers may design their access offices by placingS/BCs and MGWs such that the majority of calls between IP based UEs andTDM based PSTN phones have bearer path traversing through collocatedS/BCs and MGWs. Thus, the network can be designed to handle a smallerfraction of calls bearer path traversing an S/BC and an MGW in differentaccess offices. For example, the network may handle only 10% of callshave bearer path traversing an S/BC and an MGW in different accessoffices.

However, if a UE is unable to register with the S/BC that normallyprovides services to the UE or it loses connectivity with that S/BC,then the UE may register at another S/BC and continue accessingservices. The re-registering via another S/BC is referred to as accessoffice failover. When a UE re-registers via another S/BC, the UE isreferred to as “re-homed” at another S/BC. The re-homed UEs may continueoriginating and receiving calls to/from the PSTN phones using the MGWand S/BC in different access offices. For example, if the UE wastypically calling PSTN phones in area code 212 and the MGW handling areacode 212 was located in the same access office as the S/BC at which theUE was normally registered, after failing over by registering viaanother S/BC located at another access office, the UE typically willcontinue to call phone numbers in the same area code 212. The majorityof calls bearer path to/from re-homed UEs will flow via the new S/BC andan MGW located in different access offices. The functions of the MGW areretained in the original access office.

A service provider may enable an access office to serve as a designatedprotection site for another access office. For example, a first accessoffice may have a second access office as its designated protectionsite. If a network failure affects the first access office, customerswho typically access the first access office may utilize the secondaccess office. However, in some failure scenarios, the public networkconnection to an access office may be affected by a failure while theinternal portion is functioning normally. A large number of UEs may thenfail over (and are re-homed) to a protection site, thereby resulting inan access office failover event. An access office failover event refersto a network event in which a large number or percentage of UEs thatpreviously were registered at one or more S/BCs in a first accessoffice, suddenly re-register at one or more S/BCs located at an accessoffice serving as a protection site for the first access office.

As discussed above, the majority of PSTN calls to/from the re-homed UEsare likely from/to area codes currently serviced by the MGW in UE'soriginal home access office. Since these calls require more bandwidth atthe re-homed access office, an access office failover event may resultin the network being overloaded, or performance being degraded for allcalls. For example, calls that are normally handled by the protectionsite may experience increased delay, packet loss, etc.

In one embodiment, the present method initiates usage of a codec forre-homed calls, wherein the codec uses a lower bandwidth. For example,if the threshold for usage of bandwidth is exceeded for a second accessoffice that serves as a protection site for a first access office, themethod may initiate usage of a codec with lower bandwidth only for thecalls that are re-homed from the first access office. The usage of thecodec with lower bandwidth for re-homed calls may be applied on newcalls, existing calls, or both.

In one embodiment, the processes performed by the NMCs may beimplemented at a centralized location, e.g., a national data center, aserver office or an operation center. The centralized implementation iscapable of providing the same functions as discussed above in thedistributed implementation. However, in order to be able to handleevents that may occur in some particular areas that causes networkoverload in some particular access offices, the NMC can be implementedwith a map that shows which NPA (or NPA-NXX) codes will be impacted if aparticular NWP reports network resource issues. The mapping of the NWPto NPA or NPA-NXX codes can be provisioned via NMC configurationinterfaces and can be stored within the NMC.

In one embodiment, the method may provide a plurality of thresholds forinvoking usage of a codec with a lower bandwidth for various types oftraffic. For example, different thresholds can be set for invoking theusage of lower bandwidth on all calls, only for re-homed calls, only fornew calls, and so on. That is, the conservation of bandwidth may beapplied based on new calls versus existing calls, re-homed trafficversus traffic from the same access office, or any combination thereof.

In one embodiment, the method is also able to detect that the callvolume and/or traffic load has dropped to or below a predeterminedthreshold. For example, the method may detect that a node is operatingonly at 50% of capacity. Upon detecting the available capacity, themethod may then discontinue the usage of the codec with the lowerbandwidth. That is, the method may stop bandwidth conservation andenable usage of other codec standards. For the above example, existingand/or new calls may begin or return to using the G.711 codec to achievebetter voice quality.

In one embodiment, the predetermined threshold for initiating usage of acodec with a lower bandwidth and the predetermined threshold fortermination of the usage of the codec with the lower bandwidth may bedifferent. For example, the method may initiate usage of a codec with alower bandwidth when the node reaches 90% of capacity, whereas the nodewill return to another codec (e.g., a higher bandwidth codec) when thenode falls below 70% of capacity. Another variation to this embodimentis where the method will only take the orange level action as discussedabove after receiving “N” consecutive orange alerts from the NWPs in “M”seconds, otherwise continues to act as if receiving yellow alert.Similarly, the method will only take green level action after “K”seconds has elapsed since receiving the green alert from all NWPs in thesame access office without receiving other new yellow or orange alerts.These approaches will provide more stability in that the method is nottoo sensitive to transient network conditions.

In another embodiment, the same threshold may be used. For example, themethod may initiate usage of a codec with a lower bandwidth when thenode is operating at or above 80% of capacity and it will return toanother codec (e.g., a higher bandwidth codec) when the node falls below80% of capacity.

In one embodiment, the method for mitigating an overload can beimplemented with redundancy. For example, the method may deployredundant NMCs, wherein the redundancy provides one primary NMC and atleast one backup NMC. For example, a network condition, e.g., a failureor degradation, may affect the availability of the primary NMC. Themethod may then enable one of a plurality of backup NMCs to gatheralerts from the NWPs while the network condition is being remedied. Inone embodiment, the backup NMC can be a hot standby NMC, i.e., ready tooperate immediately when it is needed.

Note that the specific types of codecs (e.g., G.711 and G.728) describedabove are provided only as examples and should not be deemed aslimitations of the disclosure. As such, the teachings of the currentdisclosure can be used by broadly changing from any first codec to anysecond codec, wherein the second codec has a lower bandwidth usage ascompared to that of the first codec, and vice versa.

Referring back to FIG. 2, the service provider may implement NWPs in CEs264 and 294, S/BCs 262 and 292 located in the access offices 121 and124. Similarly, the service provider may implement NMCs 266 and 296 inthe access offices 121 and 124, respectively. The NMC 266 communicateswith CE 264 and S/BC 262 for receiving alerts and mitigating an overloadin access office 121. Similarly, the NMC 296 communicates with CE 294and S/BC 292 for receiving alerts and mitigating an overload in theaccess office 124. Thus, NMCs 266 and 296 monitor the network fortraffic overload by receiving alerts from the various devices that haveNWPs.

In one example, the access office 121 may become overloaded following afailover from the access office 124. The NMC 266 may then receive analert from one or more NWPs, e.g., NWPs in CE 264, S/BC 262, indicatingthat a predetermined threshold for bandwidth usage is either reached orexceeded.

The NMC 266 may then initiate usage of a codec with a lower bandwidthaccording to predetermined criteria. For example, in one embodiment thecriteria may specify one or more thresholds as to when a switch to adifferent codec will be triggered. In fact, the criteria may specifywhich portions or types of the traffic, (e.g., all calls, only newcalls, only existing calls, only calls to/from re-homed subscribers, andso on) is to use the codec with the lower bandwidth when a specificthreshold is exceeded. For example, the NMC 266 sends a command to theNMC agent(s) 241 and 251 implemented within a MGCF to effect the changein the type of codec being used. In one example, the NMC 266 may send acommand that specifies new calls will use a codec with a lowerbandwidth. In another example, the NMC 266 may send a command thatspecifies that all calls will use a codec with a lower bandwidth, and soon.

However, if the threshold for returning to the usage of the originalcodec is reached, then the method may then turn-off usage of the codecwith a lower bandwidth. For example, once the overload condition haspassed, existing and/or new calls may then resume using the originalcodec that may require more bandwidth. For example, the NMC 266 maynotify the NMC agent(s) to resume usage of a normal codec. In this way,the present disclosure is able to address an overload condition byselectively changing the codecs that are used to support calls.

In one embodiment, the NMC agents provide a command interface to receiveand confirm receipt of commands from the NMC. For example, it can beimplemented as Simple Object Access Protocol (SOAP)/Extensible MarkupLanguage (XML) interface or other interfaces such as applicationprogramming interfaces (APIs). To illustrate, on receiving a command,“new calls use normal codec”, on the following NPA (NPA-NXX) codes, theNMC agent will inform the MGC that it can resume the use of a normalcall processing logic on all incoming and outgoing calls involving thespecified NPA or NPA-NXX codes, e.g., with respect to the use of anormal codec.

In another example, on receiving a command, “new calls use lowestcodec”, on the following NPA (NPA-NXX) codes, the NMC agent will informthe MGC that when setting up a new call involving the specified NPA orNPA-NXX codes, a lowest possible codec should be used. Morespecifically, for a call originating by the NGN UE, the MGC shouldrespond by choosing the lowest codec offered by the UE in the SDPportion of the SIP message, whereas for a call originated by a PSTNuser, the MGC should construct an Invite Message to the called NGN UE byoffering the lowest codec supported.

In yet another example, on receiving a command, “all calls use lowestcodec” on the following NPA or (NPA-NXX) codes, the NMC agent willinform the MGC that when setting up a new call involving the specifiedNPA or NPA-NXX codes, a lowest possible codec should be used. Inaddition, the NMC agent will inform the MGC to initiate SIP mid callprocedures to switch to the lowest possible codec for all existing callsinvolving the same NPA or (NPA-NXX) codes and are not using the lowestpossible codec.

In one embodiment, the processes performed by the NMCs may beimplemented at a centralized location, e.g., a national data center, aserver office or an operation center. The NMC in a centralized locationmay then be responsible for monitoring and controlling traffic for theentire network. The centralized implementation is capable of providingthe same functions as discussed above in the distributed implementation.However, in order to be able to handle massive calling events that mayoccur in some particular areas, the NMC can be implemented with mappinginformation that shows which NPA (or NPA-NXX) codes will be impacted ifa particular NWP reports network resource issues. The mapping of the NWPto NPA or NPA-NXX codes can be provisioned via NMC configurationinterfaces and can be stored within the NMC.

FIG. 3 illustrates an exemplary network 300 for mitigating an overloadin a network via centralized NMCs. The network 300 is similar to network200 except for the fact that the NMCs are located in the server offices.As such, the descriptions of similar components in FIG. 3 to those ofFIG. 2 are provided above. In one embodiment, the NMCs 345 and 355 canbe deployed in the server offices 131 and 132, respectively. The NMCs345 and 355 are responsible for the entire network. The mapping of theNWP to NPA or NPA-NXX codes may then be provisioned via NMCconfiguration interfaces and may be stored within the NMCs 345 and 355.If a network usage burst is detected, the centralized NMCs 345 and 355may inform NMC agents to take action. In one embodiment, the NMC 345 isthe primary NMC, whereas the NMC 355 is a backup NMC. In other words,the NMC 355 can be implemented as a redundant NMC.

In one embodiment, the NMC may generate notification or alarms to ahigher level network management system when it takes measures. This willprovide another level of monitoring.

FIG. 4 illustrates a flowchart of a method 400 for mitigating anoverload in a network. For example, one or more steps of method 400 canbe implemented by an NMC. Method 400 starts in step 405 and proceeds tostep 410.

In step 410, method 400 monitors the network for detecting trafficoverload, i.e., an overload condition. For example, an NMC may monitorthe network for traffic overload by receiving alerts (e.g., periodicallyor when a threshold is reached) from various devices in the network thathave NWPs. The method then proceeds to step 415.

In step 415, method 400 determines whether a network condition changehas been detected. For example, method 400 determines whether a networkcondition change has been detected. If the answer is affirmative, method400 proceeds to step 420. If the answer is negative, method 400 proceedsto step 410.

In step 420, method 400 determines if a more severe overload conditionis detected. As described earlier, there may be several levels ofthresholds. For example, if the previous monitoring indicated that therewas no overload condition, then the previous network condition isassociated with a green level. If the latest monitoring indicated thatthe threshold associated with yellow level is reached, then the methoddetermines that there is a more severe overload condition in step 420.In another example, if the previous monitoring indicated there was anoverload condition associated with the yellow level, and the latestmonitoring indicated the threshold associated with the orange level isreached, then the method determines that there is an even more severeoverload condition. In yet another example, if the previous monitoringindicated there was an overload condition associated with the orangelevel, and the latest monitoring indicated the threshold associated withthe red level is reached, then the method determines that there is avery severe overload condition. If a more severe overload condition isdetected, the method proceeds to step 430. Otherwise, the methodproceeds to step 450.

In step 430, method 400 selects a different bandwidth preservationscheme to address a more severe overload condition. In one example, themethod issues a command to enforce usage of a lower bandwidth codecrelative to the codec currently being used for new calls (e.g., yellowthreshold is reached, as described above). In one example, usage of thelower bandwidth codec is enforced for all calls (e.g., orange thresholdis reached, as described above). In one example, other, more aggressivebandwidth preservation schemes may be necessary. For example, if the redthreshold is reached, other methods such as throttling, blocking, etc.may have to be initiated. The method then proceeds to step 410 tocontinue monitoring the network.

In step 450, method 400 selects a different bandwidth preservationscheme to address the detection of a less severe overload condition. Inother words, since a network overload condition change was detected instep 415 and a more severe overload condition was not detected in step420, then the network overload condition change must be due to thedetection of a less severe overload condition.

For example, if there is no overload condition, then the method may thenissue a command to stop enforcing the usage of a lower bandwidth codec.Hence, the method may issue a command to stop enforcing the previouslybandwidth preservation scheme. In another example, the method issues acommand to stop enforcing a previously selected bandwidth preservationscheme to address an improved condition. For example, if throttling ofnew calls was previously implemented (e.g., at a red level), but thenetwork overload condition has since then improved, then the method mayissue a command to stop throttling, and continue to use a lowerbandwidth codec (e.g., an orange level or even a yellow level). Themethod then proceeds to step 410 to continue monitoring the network.

Note that the criteria for determining which portion of the traffic(e.g., all calls, only new calls, only existing calls, only re-homedcalls, and so on) is affected due to a command to enforce usage of acodec with a lower bandwidth is selectively determined. For example, oneservice provider may choose to enforce usage of a lower bandwidth codecon all calls at a lower overload condition. Another service provider,may elect to enforce the usage of a lower bandwidth codec only on newcalls regardless of the severity of the overload condition.

For example, in one embodiment, if a first threshold (e.g., 75% ofcapacity) is reached, the method may dictate that all re-homed calls areto use a lower bandwidth codec, while other types of calls can continueto use codecs with a higher bandwidth. However, if a second threshold(e.g., 85% of capacity) is reached, the method may dictate that all newcalls are to use the lower bandwidth codec as well. However, if a thirdthreshold (e.g., 90% of capacity) is reached, the method may dictatethat all existing or currently on-going calls are to use the lowerbandwidth codec as well. Finally, if a fourth threshold (e.g., 95% ofcapacity) is reached, the method may dictate that all calls,irrespective of types, are to use the lower bandwidth codec. It shouldbe noted that the threshold values provided in the above example is onlyillustrative and should not be deemed to be a limitation of the presentdisclosure. Furthermore, although the above example only discloses theusage of a higher bandwidth codec or a lower bandwidth codec, theteachings of the present disclosure is not so limited. In other words,there could be a plurality of codecs with varying bandwidth capabilitieswith more granularity than simply “higher bandwidth” or “lowerbandwidth”, where the NMC may dictate different types of codecs to beused depending on the traffic condition of the network.

Similarly, if conditions improve, there may be sufficient bandwidth toswitch to another bandwidth preservation scheme, or to deactivate theusage of a codec with a lower bandwidth codec. The criteria fordeactivation are also pre-determined by the service provider. Forexample, if a first threshold (e.g., 86% of capacity) is reached, themethod may dictate that all new calls, except for those to/from aparticular NPA.NXX can use a higher bandwidth codec, while existingcalls and calls to/from the particular NPA.NXX continue to use codecswith a lower bandwidth. However, if a second threshold (e.g., 81% ofcapacity) is reached, the method may dictate that all new calls are touse the higher bandwidth codec as well, while existing calls continue touse the lower bandwidth codec.

It should be noted that using mid-call procedure to change codec forexisting calls are relatively expensive. As such, in one embodiment,when the method steps down to a lower level, it may want to avoidimplementing the mid-call procedure to change codec. As long as themethod allows new calls to use better or higher bandwidth codec,existing calls will eventually terminated. However, in anotherembodiment, in some other services, such as those NGNs that serve manylong-lasting conference calls, it may be practical to use mid-callprocedure to switch the codec.

It should be noted that the media gateways, S/BCs, NMCs, NWPs, and othernetwork elements may be located in other types of offices. For example,a regional office may house these network elements and/or modules innetwork elements for various access offices. In addition, a PE and CEmay be located within the same physical building. As such, the pairingof a CE and a PE defines the relationship between the backbone andaccess portions of the NGN. Therefore, the above description is notintended to limit the implementation to a specific type of office orphysical structure.

It should be noted that although not specifically specified, one or moresteps of method 400 may include a storing, displaying and/or outputtingstep as required for a particular application. In other words, any data,records, fields, and/or intermediate results discussed in the method canbe stored, displayed and/or outputted to another device as required fora particular application. Furthermore, steps or blocks in FIG. 4 thatrecite a determining operation or involve a decision, do not necessarilyrequire that both branches of the determining operation be practiced. Inother words, one of the branches of the determining operation can bedeemed as an optional step.

FIG. 5 illustrates a state transition diagram 500. FIG. 5 illustrateshow the present method may transition from different overload conditionseverity levels, e.g., green, yellow, orange, and red. It should benoted that the use of various colors in this example should not beinterpreted as a limitation of the present disclosure. Any manner oflabeling the different overload condition severity levels is acceptable.

In one embodiment, the method starts at an initial state 505, e.g.,during network setup or configuration. Once the network is operational,it will enter into the green state 510. While in the green state, thenetwork does not enforce codec usage for any call session and continuesto be monitored for any potential condition change. If a networkcondition change is detected, e.g., the trigger 512 where the methodreceives an alert indicating an overload condition exceeding a thresholdfor the yellow state, then it will transition into the yellow state 520.

While in the yellow state, a lower bandwidth codec is used for new callsand the network continues to be monitored for an overload conditionchange. If an overload condition change is detected, e.g., the trigger522 where the method receives an alert indicating an overload conditionexceeding a threshold for the orange state, then it will transition intothe orange state 530. Alternatively, if an overload condition change isdetected, e.g., the trigger 514 where the method receives an alertindicating an overload condition falling below a threshold for theyellow state, then it will transition into the green state.

While in the orange state, a lower bandwidth codec is used for allcalls, i.e., new calls and existing calls, and the network continues tobe monitored for an overload condition change. If an overload conditionchange is detected, e.g., the trigger 532 where the method receives analert indicating an overload condition exceeding a threshold for the redstate, then it will transition into the red state 540. Alternatively, ifan overload condition change is detected, e.g., the trigger 524 wherethe method receives an alert indicating an overload condition fallingbelow a threshold for the orange state, then it will transition into theyellow state.

While in the red state, throttling of new calls may be implemented, andthe network continues to be monitored for an overload condition change.If an overload condition change is detected, e.g., the trigger 534 wherethe method receives an alert indicating an overload condition fallingbelow a threshold for the red state, then it will transition into theorange state.

It should be noted that although the state transition diagramillustrates the transition of states as occurring in a sequential singlestep manner, the present disclosure is not so limited. For example, themethod can be implemented where a transition may occur where ittransitions from the red level directly to the yellow level or viceversa, i.e., skipping a level. Further, the method can incorporatestabilization methods to reduce the sensitivity on transient networkcondition changes. For example, it could wait for a certain number of anetwork condition change alerts to occur in a observation time window totrigger a state transition. The manner as to how the transition willoccur can be tailored to the requirements of a particular network.

FIG. 6 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 6, the system 600 comprises a processor element 602(e.g., a CPU), a memory 604, e.g., random access memory (RAM) and/orread only memory (ROM), a module 605 for mitigating an overload in anetwork, and various input/output devices 606 (e.g., storage devices,including but not limited to, a tape drive, a floppy drive, a hard diskdrive or a compact disk drive, a receiver, a transmitter, a speaker, adisplay, a speech synthesizer, an output port, and a user input device(such as a keyboard, a keypad, a mouse, alarm interfaces, power relaysand the like)).

It should be noted that the teachings of the present disclosure can beimplemented in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a general-purposecomputer or any other hardware equivalents. In one embodiment, thepresent module or process 605 for mitigating an overload in a networkcan be loaded into memory 604 and executed by processor 602 to implementthe functions as discussed above. As such, the present method 605 formitigating an overload in a network (including associated datastructures) of the present invention can be stored on a non-transitorycomputer readable storage medium, e.g., RAM memory, magnetic or opticaldrive or diskette and the like.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for monitoring a traffic overloadcondition for traffic in a network, the method comprising: monitoring,by a processor of a network monitor, the network for the trafficoverload condition; determining, by the processor, whether a more severetraffic overload condition or a less severe traffic overload conditionis detected as compared to a previous traffic overload condition; andissuing, by the processor, a command to a network monitor and controlleragent, wherein the command is used to select a different bandwidthpreservation scheme, when the more severe traffic overload condition orthe less severe traffic overload condition is detected, wherein thedifferent bandwidth preservation scheme is based on a selection of acodec type, wherein the different bandwidth preservation scheme isapplied to a portion of the traffic, wherein the portion of the trafficcomprises re-homed calls.
 2. The method of claim 1, wherein thedetermining is based on a threshold.
 3. The method of claim 2, whereinthe threshold is associated with an overload condition severity level.4. The method of claim 3, wherein the overload condition severity levelis associated with a particular bandwidth preservation scheme as to amanner of processing various types of traffic.
 5. The method of claim 1,wherein the monitoring the network for the traffic overload conditioncomprises receiving an alert from a network element.
 6. The method ofclaim 5, wherein the network element comprises a session bordercontroller.
 7. The method of claim 5, wherein the network elementcomprises a media gateway.
 8. The method of claim 5, wherein the networkelement comprises a router.
 9. The method of claim 5, wherein the alertis generated by a network watch point.
 10. A non-transitorycomputer-readable medium storing a plurality of instructions which, whenexecuted by a processor of a network monitor, cause the processor toperform operations for monitoring a traffic overload condition fortraffic in a network, the operations comprising: monitoring the networkfor the traffic overload condition; determining whether a more severetraffic overload condition or a less severe traffic overload conditionis detected as compared to a previous traffic overload condition; andissuing a command to a network monitor and controller agent, wherein thecommand is used to select a different bandwidth preservation scheme,when the more severe traffic overload condition or the less severetraffic overload condition is detected, wherein the different bandwidthpreservation scheme is based on a selection of a codec type, wherein thedifferent bandwidth preservation scheme is applied to a portion of thetraffic, wherein the portion of the traffic comprises re-homed calls.11. The non-transitory computer-readable medium of claim 10, wherein thedetermining is based on a threshold.
 12. The non-transitorycomputer-readable medium of claim 11, wherein the threshold isassociated with an overload condition severity level.
 13. Thenon-transitory computer-readable medium of claim 12, wherein theoverload condition severity level is associated with a particularbandwidth preservation scheme as to a manner of processing various typesof traffic.
 14. The non-transitory computer-readable medium of claim 10,wherein the monitoring the network for the traffic overload conditioncomprises receiving an alert from a network element.
 15. Thenon-transitory computer-readable medium of claim 14, wherein the networkelement comprises a session border controller.
 16. The non-transitorycomputer-readable medium of claim 14, wherein the network elementcomprises a media gateway.
 17. The non-transitory computer-readablemedium of claim 14, wherein the network element comprises a router. 18.The non-transitory computer-readable medium of claim 14, wherein thealert is generated by a network watch point.
 19. An apparatus formonitoring a traffic overload condition for traffic in a network, theapparatus comprising: a network monitor comprising a processor; and anon-transitory computer-readable medium storing a plurality ofinstructions which, when executed by the processor, cause the processorto perform operations, the operations comprising: monitoring the networkfor the traffic overload condition; determining whether a more severetraffic overload condition or a less severe traffic overload conditionis detected as compared to a previous traffic overload condition; andissuing a command to a network monitor and controller agent, wherein thecommand is used to select a different bandwidth preservation scheme,when the more severe traffic overload condition or the less severetraffic overload condition is detected, wherein the different bandwidthpreservation scheme is based on a selection of a codec type, wherein thedifferent bandwidth preservation scheme is applied to a portion of thetraffic, wherein the portion of the traffic comprises re-homed calls.20. The apparatus of claim 19, wherein the monitoring the network forthe traffic overload condition comprises receiving an alert from anetwork element having a network watch point.